Modules can have a special variable named __all__ to restrict what variables are imported when using from mymodule import *.
Given the following module:
# mymodule.py
__all__ = ['imported_by_star']
imported_by_star = 42
not_imported_by_star = 21
Only imported_by_star is imported when using from mymodule import *:
>>> from mymodule import *
>>> imported_by_star
42
>>> not_imported_by_star
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'not_imported_by_star' is not defined
However, not_imported_by_star can be imported explicitly:
>>> from mymodule import not_imported_by_star
>>> not_imported_by_star
21